Nerve interface electrode with fibers for insertion between nerve fascicles

ABSTRACT

A nerve interface electrode has a plurality of conductive fibers. The fibers have a nonconductive sheath ( 108 ) surrounding a conducting wire. A conducting region ( 105 ) of the wire is exposed to the interior of the nerve ( 200 ). The fibers are configured for insertion between fascicles ( 204 ) of the nerve. In other teachings, a layer of polymer material configured to switch from a high strength/tensile modulus state to a low strength/tensile modulus state upon introduction of the fibers into the nerve is disposed on the fibers.

PRIORITY

This application claims priority to U.S. Provisional Application No.61/478,664, filed on Apr. 25, 2011, which is incorporated by referenceas if fully set forth herein.

FIELD OF THE INVENTION

This disclosure is directed to nerve interfaces, such as peripheralnerve electrodes.

BACKGROUND

Nerve interfaces such as peripheral nerve electrodes allow recording andstimulation of nerve activity. For example, electrodes may be used toactivate nerves connected to a particular muscle. One of the mostimportant aspects of nerve interfaces is their ability to selectivelyactivate or record nerve signals. For example, selective activation ofsingle or small groups of fascicles can assist in “pure” activation ofcertain muscle groups, such as knee extensor muscles, with minimalactivation of other non-synergistic muscle groups, for example hipflexors. In some instances, selective activation or recording of smallergroups or individual fascicles is desirable.

SUMMARY

In one embodiment, a nerve interface electrode comprising a plurality ofconductive fibers is disclosed. The fibers comprise a nonconductivesheath surrounding a conducting wire. A conducting region of the wire isexposed to the interior of the nerve. The fibers are configured forinsertion between fascicles of the nerve. In other embodiments, a layerof polymer material configured to switch from a high strength/tensilemodulus state to a low strength/tensile modulus state upon introductionof the fibers into the nerve is disposed on the fibers. Thisconfiguration allows the fibers to be rigid prior to insertion butbecome flexible after insertion into the nerve.

In another embodiment of the present disclosure, a method of implantinga nerve interface electrode is disclosed. An electrode having multipleconductive fibers configured to flexibly disperse in a nerve in theregion between the fascicles is selected. The fibers are insertedthrough the epineurium and into the nerve. The fibers then electricallystimulate the fascicles or record electrical activity within the nerve.

BRIEF DESCRIPTION OF THE DRAWINGS

It will be appreciated that the illustrated boundaries of elements inthe drawings represent only one example of the boundaries. One ofordinary skill in the art will appreciate that a single element may bedesigned as multiple elements or that multiple elements may be designedas a single element. An element shown as an internal feature may beimplemented as an external feature and vice versa.

Further, in the accompanying drawings and description that follow, likeparts are indicated throughout the drawings and description with thesame reference numerals. The figures may not be drawn to scale and theproportions of certain parts have been exaggerated for convenience ofillustration.

FIG. 1 illustrates an exemplary nerve interface 100.

FIG. 2 illustrates a nerve interface 100 inserted through the epineurium202 of nerve 200.

FIG. 3 illustrates a cross-sectional view along the nerve 200 afterinsertion of fibers 104.

FIG. 4 illustrates a cross-sectional side view along the nerve 200 afterinsertion of fibers 104.

FIG. 5 illustrates exemplary method of implanting nerve interface 100.

FIG. 6 illustrates a nerve interface 100 inserted through the epineurium202 of nerve 200 with the aid of guide 600.

FIG. 7 illustrates a graph of a computer simulation for a single contactplaced within the nerve at various distances from the target fascicle.

FIG. 8 illustrates cross sections of a simulated nerve under variouscontact placements and various activation levels.

FIG. 9 illustrates a graph of subfascicular selectivity at certainpercent levels of selectivity amplitude.

FIG. 10 illustrates locations of activations for contacts 1000, 1002.

FIGS. 11-13 illustrate a graph of the results of stimulations havingmultiple contact points in single sciatic nerve of a rabbit.

DETAILED DESCRIPTION

Certain terminology will be used in the following description forconvenience in describing the figures will not be limiting. The terms“upward,” “downward,” and other directional terms used herein will beunderstood to have their normal meanings and will refer to thosedirections as the drawing figures are normally viewed.

FIG. 1 illustrates a nerve interface 100 according to the presentdisclosure. The illustrated interface 100 has a housing 102 from whichfibers 104 extend. In the illustrated embodiment, the fibers 104 have anonconductive sheath 108 that covers a core of conductive wire 106 thatis coupled to the control unit 112. Nonconductive sheath 108 covers asubstantial portion of the surface of the wire 106, exposing only aportion of wire 106, corresponding to the conducting region 105, throughsheath opening 114. The opening 114 may take a variety of shapes andsizes, but preferably exposes a conducting region 105 that faces asubset of the interior of the nerve 200, making the fiber 104 able, forexample, to emit current in the direction the conducting region 105faces while minimizing current emitted in other directions. Asillustrated in FIG. 1, the sheath opening 114 exposes only a smallportion of wire 106, allowing the fibers 104 to be directionallysensitive to received electrical signals and directionally selective intransmitting electrical signals. Throughout this disclosure, referencemay be made to fibers 104 as stimulating nerves, while in otherinstances, fibers 104 may be described as recording nerve signals. Itshould be noted that, while the preferred embodiment stimulates andrecords electrically, the nerve interface need not be so limitedaccording to the present disclosure. The fibers may be configured todetect, for example, different forms of energy transfer reflectingneuronal activity and communication, such as detection of theconcentration particular chemicals. It should also be noted that theplacement of the nerve interface 100 described in the present disclosurewith regard to nerve stimulation will also be applicable in recordingnerve signals.

Interface 100 is connected to control unit 112 by lead 110. Fibers 104are each connected to the control unit 112, which may include monitoringcircuitry, electrical signal generating circuitry, and a user interface.Several alternative implementations of control unit 112 and leads 110are well known in the art and will not be discussed further herein.Fibers 104 have a longitudinal length much larger than the thickness ofthe generally cylindrical fibers 104 illustrated in the presentdisclosure. It should be noted that the fibers 104 illustrated in thecurrent disclosure are not drawn to scale, and will preferably have amuch thinner size relative to, for example, the nerve 200 shown in FIG.2. Fibers 104 may have different cross-sectional shapes, such aselliptical, polygonal, or a combination of multiple shapes. In suchcases, the length of fibers 104 will be much larger than acharacteristic thickness of fibers 104 having such cross-sectionalshapes.

As shown in FIG. 2, the fibers 104 are inserted into the nerve 200through the epineurium membrane 202. As will be discussed further belowin connection with FIG. 3, insertion of the fibers 104 through theepineurium 202 exposes the portion of the fibers 104 that has penetratedthe epineurium 202, which includes the conducting region 105 of thefibers 104, to the interior of the nerve 200. Fibers 104 may be used topierce the epineurium 202. In such cases, the fibers 104 may beconfigured with sharp tips in order to more easily pierce the epineurium202. The thinness of fibers 104 will aid in the insertion of the fibers104 and minimize the disturbance to the nerve 200. Alternatively,separate incisions through which the fibers 104 are inserted may be madeprior to insertion of fibers 104. Endoscopic and minimally invasiveimplantation are exemplary methods of implantation of fibers 104.

FIG. 3 illustrates a cross-section of a peripheral nerve 200 afterinsertion of fibers 104. While a peripheral nerve 200 is used forpurposes of illustration, the interface 100 according to the presentinvention will also be applicable to other types of nerve tissue, suchas nerve tissue found in the central nervous system. The nerve 200 issurrounded by the epineurium membrane 202, or simply “epineurium.” Thenerve 200 contains several fascicles 204, which comprise bundles ofaxons. Each fascicle 204 is surrounded by a perineurium membrane 206, orsimply “perineurium.” FIG. 3 also illustrates the placement of fibers104 throughout the interior of the nerve 200. Fibers 104 in the nerve200 are flexible and so spread out, distributing themselves throughoutthe interior of the nerve 200 in the area between the fascicles 204. Thefibers 104 do not penetrate the perineurium membrane 206, whichminimizes trauma to the nerve 200. The distribution of fibers 104between the fascicles 204 allows for improved selectivity in the controland measurement of individual fascicles 204 and their electricalactivity.

As shown in FIG. 3, several conducting regions 105 of fibers 104 comeinto contact with perineurium membranes 206 of fascicles 204, whileother conducting regions 105 are disposed adjacent but not in contactwith a fascicles 206. In such an arrangement, fibers 104 can conductelectrical current in a directed manner, in the direction the conductingregions 105 face. This allows for relatively increased current densityin the direction the conducting region 105 faces. This arrangement alsoallows for fibers 104 to be directionally sensitive when recordingelectrical activity. Fibers 104 will be most sensitive to electricalactivity received from the direction the conducting region 105 faces.Further, in the illustrated configuration, fibers 104 may be placednearby fascicles 204 located centrally within the nerve 200. Activationof an individual fiber 104 may stimulate a single fascicle 204 ormultiple fascicles 204. This may in turn result in recruitment ofadditional fascicles 204 depending on the distribution of fascicles 204in the nerve. Likewise, multiple fibers 104 may be activated, which mayresult in stimulation of multiple fascicles 204.

In addition to directed stimulation of individual fascicles 204, thefibers 204 may generate a desired electrical field (“field shaping”)within the nerve 200 by selectively applying the appropriate level ofelectrical current to each of the fibers 104, the fibers 104 may createan electrical field that may selectively activate one or more fascicles204, including fascicles 204 that are not adjacent to or in directcontact with a fiber 104.

In order to disperse among the spaces between the fascicles 204, thefibers 104 are preferably flexible. Flexibility allows the fibers 104 todisperse within the nerve 200, which allows for broader distribution offibers 104, and therefore more selective control or recording offascicles 204. However, flexibility can make insertion of the fibers 104through the epineurium 202 more difficult. In one embodiment, the fiber104 is coated with a layer of polymer nanocomposite material thatswitches from a high tensile modulus and strength to a low modulus andstrength in response to introduction to the interior of the nerve 200.This layer may be part of the nonconductive sheath 108 or may be aseparate layer. In the high tensile modulus/strength state, the polymernanocomposite renders the fibers 104 rigid enough to puncture theepineurium 202. Such materials and the manner in which they may bemanufactured are disclosed in U.S. Published Patent Application Nos.2009/0318590 and 2008/0242765, incorporated herein by reference. Forexample, nanocomposite such as ethylene oxide-epichlorohydrin (“EO-EPI”)combined with a cellulose matrix can exhibit high tensile strength inthe absence of solvent. When an appropriate solvent, preferably ahydrogen-bond forming solvent, is introduced to the nanocomposite, theinteractions giving the nanocomposite its strength are “switched off” bythe competitive binding of the solvent. Other host polymers orcopolymers may include, but are not limited to, various alkylene oxidepolymers and copolymers such as ethylene oxide, propylene oxide,copolymers of ethylene oxide and epichlorohydrin and/or other monomers;a vinyl aromatic (co)polymer such as polystyrene and styrene copolymers;polyolefin polymers or copolymers such as polyethylene andpolypropylene; diene polymers and copolymers, such as cis-polybutadiene;polyacrylates and acrylate copolymers, such as methyl methacrylate;polyamides; and polyester polymers or copolymers such as poly(vinylacetate) or polycaprolactone.

FIG. 4 illustrates a cross-sectional side view of a single fiber 104inserted through the epineurium 202 and disposed adjacent a fascicle204. In the illustrated embodiment, the fiber 104 is inserted throughthe epineurium 202 at an acute angle relative to the direction of thenerve 200. This configuration allows the fibers 104 to orient themselvesparallel with the fascicles 204. As shown in FIG. 4, the conductingregion 105 is disposed adjacent the perineurium membrane 206 of fascicle204.

As shown in FIG. 5, in one method of stimulation and/or recording ofperipheral nerve electrical activity, an interface 100 having multipleconductive fibers 104 configured to flexibly disperse in the nerve 200in the region between the fascicles 204 is selected in step 500. Inanother embodiment, an interface 100 having additional qualities such asfibers 104 each having a sheath 108 configured to switch from a hightensile modulus and strength to a relatively low tensile modulus andstrength upon insertion into the nerve 200, thereby permitting thefibers 104 to flexibly disperse in the region in the nerve 200 betweenthe fascicles 204, is selected. In yet another alternative embodiment,an interface 100 configured for insertion into a peripheral nerve isselected. In the illustrated embodiment, the electrode is then insertedthrough the epineurium 202 and into the nerve in step 510. Step 510 maybe accomplished by a variety of approaches, such as an open surgicalprocedure, or alternatively a minimally invasive approach. In step 520,upon dispersal of the fibers 104 in the nerve 200 and between thefascicles 204, the fibers 104 record and/or stimulate nerve 200activity.

FIG. 6 illustrates an alternative embodiment of nerve interface 100having a guide 600 that assists in insertion of fibers 104. The guideprovides additional rigidity to the fibers 104 as they are inserted, forexample when using the fibers 104 to penetrate the epineurium 202. Theguide 600 reduces the length of fibers 104 that must kept rigid forinsertion into nerve 200. The guide 600 may be placed adjacent theepineurium membrane 202 prior to insertion of fibers 104.

FIGS. 7 and 8 show the results of a computer simulation demonstratingthe selectivity of a single contact placed within the nerve and atvarious distances from the target fascicle. The plot shown in FIG. 7,illustrates the selectivity for contacts directly next to the fascicleshown as line 702, 10 um from the target fascicle shown as line 704, 50um from the target fascicle shown as line 706, and 100 um from thetarget fascicle shown as line 708 as compared to a contact on thesurface of the nerve shown as line 710. A selectivity value of 100reflects perfect selectivity for the target fascicle and can be achievedif the contact is in direct contact with the fascicle. The selectivitydrops, but is still desirable as the distance between the fascicle andcontact is increased. FIG. 8 illustrates the areas of activation at thepoint indicated by the grayscale 800 for two contact-fascicleseparations. The two columns correspond to contact placement adjacent tothe target fascicle and 100 um from the target fascicle, which in all ofthe simulations in FIG. 8 is the upper right fascicle 802. The threerows correspond to higher 20%, 60% and 100% of target activation.

FIGS. 9 and 10 illustrate results of a simulation for sub-fascicularselectivity. FIG. 9 shows a graph of subfascicular selectivity atcertain percent levels of selectivity amplitude. The line 900 representsinterfascicular placement while line 902 represents intrafascicularplacement. FIGS. 9 and 10 show that each of the contacts 1000, 1002outside the nerve 1001 excite about 80% of the fibers in the closesthalf of the fascicle without activation of any fibers on the other side.FIG. 10 illustrates the locations of activations, with activated fibersshown with an x, while non-activated fibers are shown with an ovalshape. For example, fibers 1004 activated by contact 1000 are on theright side of the nerve 1001, while fibers 1006 activated by contact1002 are isolated on the left side of the nerve 1001. The simulationsalso show that two electrodes outside of the fascicle are as selectiveas two contacts placed directly within the fascicle.

FIGS. 11 through 13 illustrate the results of a stimulation of multiplecontact points in single sciatic nerve of a rabbit. The effected musclesare the Tibialis Anterior muscle, abbreviated “TA,” the LateralGastrocnemius muscle, abbreviated “LG,” the Medial Gastrocnemius muscle,abbreviated “MG” and the “Soleus” muscle. As shown in FIGS. 11 through13, three completely different recruitments are possible. Thus, multiplepoint sources within the nerve may produce multiple different outputs.

For the purposes of this disclosure and unless otherwise specified, “a”or “an” means “one or more.” To the extent that the term “includes” or“including” is used in the specification or the claims, it is intendedto be inclusive in a manner similar to the term “comprising” as thatterm is interpreted when employed as a transitional word in a claim.Furthermore, to the extent that the term “or” is employed (e.g., A or B)it is intended to mean “A or B or both.” When the applicants intend toindicate “only A or B but not both” then the term “only A or B but notboth” will be employed. Thus, use of the term “or” herein is theinclusive, and not the exclusive use. See, Bryan A. Garner, A Dictionaryof Modern Legal Usage 624 (2d Ed. 1995). Also, to the extent that theterms “in” or “into” are used in the specification or the claims, it isintended to additionally mean “on” or “onto.” Furthermore, to the extentthe term “connect” is used in the specification or claims, it isintended to mean not only “directly connected to,” but also “indirectlyconnected to” such as connected through another component or multiplecomponents. As used herein, “about” will be understood by persons ofordinary skill in the art and will vary to some extent depending uponthe context in which it is used. If there are uses of the term which arenot clear to persons of ordinary skill in the art, given the context inwhich it is used, “about” will mean up to plus or minus 10% of theparticular term. From about X to Y is intended to mean from about X toabout Y, where X and Y are the specified values.

While the present disclosure illustrates various embodiments, and whilethese embodiments have been described in some detail, it is not theintention of the applicant to restrict or in any way limit the scope ofthe claimed invention to such detail. Additional advantages andmodifications will readily appear to those skilled in the art.Therefore, the invention, in its broader aspects, is not limited to thespecific details and illustrative examples shown and described.Accordingly, departures may be made from such details without departingfrom the spirit or scope of the applicant's claimed invention. Moreover,the foregoing embodiments are illustrative, and no single feature orelement is essential to all possible combinations that may be claimed inthis or a later application.

1. A nerve interface electrode comprising: A plurality of conductivefibers having a nonconductive sheath surrounding a conducting wire: aconducting region configured to be exposed to an interior of a nerve,the plurality of fibers configured for insertion between fascicles ofthe nerve.
 2. The nerve interface electrode of claim 1 wherein theconducting region is configured to be exposed to an interior of aperipheral nerve, the plurality of fibers configured for insertionbetween fascicles of the peripheral nerve.
 3. The nerve interfaceelectrode of claim 1 further comprising: a layer of polymer materialdisposed the fibers and configured to switch from a high strength ortensile modulus state to a low strength or tensile modulus state uponintroduction of the fibers into the peripheral nerve.
 4. The nerveinterface electrode of claim 3 wherein the layer of polymer materialincludes oxide-epichlorohydrin and a cellulose matrix.
 5. The nerveinterface electrode of claim 3 wherein the layer of polymer materialincludes an alkylene oxide polymer or copolymer.
 6. The nerve interfaceelectrode of claim 5 wherein the layer of polymer material includes atleast one of ethylene oxide, propylene oxide, ethylene oxide copolymerand epichlorohydrin.
 7. The nerve interface electrode of claim 3 whereinthe layer of polymer material includes a vinyl aromatic polymer orcopolymer.
 8. The nerve interface electrode of claim 7 wherein the layerof polymer material includes at least one of polystyrene and styrenecopolymer.
 9. The nerve interface electrode of claim 3 wherein the layerof polymer material includes a polyolefin polymer or copolymer.
 10. Thenerve interface electrode of claim 3 wherein the layer of polymermaterial includes a diene polymer or copolymer.
 11. The nerve interfaceelectrode of claim 1 wherein the sheath defines a sheath opening, theconducting region disposed at the sheath opening.
 12. A nerve interfaceelectrode comprising: A plurality of conductive fibers having anonconductive sheath surrounding a conducting wire: a conducting regionconfigured to be exposed to an interior of a nerve, the plurality offibers configured for insertion between fascicles of the nerve; and, alayer of polymer material disposed the fibers and configured to switchfrom a high strength or tensile modulus state to a low strength ortensile modulus state upon introduction of the fibers into the nerve 13.A method of implanting a nerve interface electrode comprising: selectingan electrode having multiple conductive fibers configured to flexiblydisperse in a nerve in the region between fascicles of the nerve;inserting the fibers through the epineurium and into the nerve; and,electrically stimulating or recording one or more fascicles.
 14. Themethod of claim 13, wherein the selecting step comprises selecting anelectrode having fibers having an outer layer configured to switch froma high tensile modulus and strength to a low tensile modulus andstrength upon insertion into the nerve.
 15. The method of claim 13,wherein the selecting step further comprises: selecting an electrodeconfigured to flexibly disperse in a peripheral nerve.